bad argument #2 to 'strformat' #42

2x AstralKeys\Lists\Friends-Friends.lua:136: bad argument #2 to 'strformat' (string expected, got nil)
[string "=[C]"]: ?
[string "@AstralKeys\Lists\Friends-Friends.lua"]:136: in function `method'
[string "@AstralKeys\Events.lua"]:84: in function <AstralKeys\Events.lua:80>

Locals:
(*temporary) = "%s-%s"
(*temporary) = nil
(*temporary) = "ZirkeldesCenarius"
(*temporary) = "string expected, got nil"